Ink jet recording apparatus, sub-tank unit adapted thereto, and ink droplet ejection capability recovery method

Abstract

An inkjet recording apparatus is provided, which comprises a sub-tank unit mounted on a carriage for supplying ink to an ink jet record head and an ink replenishment unit connected to a main tank installed on a housing by a duct and being able to be connected to and disconnected from the sub-tank unit. The sub-tank unit comprises an ink injection port and an exhaust port that are communicated with an ink storage chamber via self-seal type valve means, and a valve mechanism for opening and closing the exhaust port based on a liquid level of ink, wherein ink is supplied to the ink storage chamber by negative pressure from negative pressure generation means for sucking air through the exhaust port. Also provided is an ink droplet ejection capability recovery method for a recording head of an ink jet recording apparatus for determining an amount of ink remaining in the sub-tank unit, replenishing the sub-tank unit with ink from the main tank, and performing a recovery operation.

What is claimed is:  
     
       1. An ink jet recording apparatus comprising: a sub-tank unit, mounted on a carriage, for supplying ink to an ink jet record head; and an ink replenishment unit that is connected to a main tank installed in a housing and that is connectable to and disconnectable from said sub-tank unit, 
       wherein said sub-tank unit includes:  
       an ink injection port and an exhaust port communicating with an ink storage chamber through self-seal type valve means; and  
       a valve mechanism for opening and closing the ink injection port or the exhaust port based on a liquid level of ink;  
       wherein ink is supplied to the ink storage chamber by negative pressure of negative pressure generation means for sucking air through the exhaust port.  
     
     
       2. The ink jet recording apparatus as claimed in  claim 1 , wherein: 
       said sub-tank unit comprises a single container divided into a plurality of chambers by a wall or walls;  
       said sub-tank unit has, for each of the chambers, the ink injection port and the exhaust port communicating with the respective ink storage chamber through the self-seal type valve means, and the valve mechanism for opening and closing the ink injection port or the exhaust port based on the liquid level of the ink,  
       wherein the ink is supplied to the respective ink storage chamber by negative pressure produced by sucking air through the exhaust port.  
     
     
       3. The ink jet recording apparatus as claimed in  claim 1 , wherein valve means closed by said ink replenishment unit is connected between said sub-tank unit and the record head. 
     
     
       4. The ink jet recording apparatus as claimed in  claim 1 , wherein the valve mechanism includes a float member. 
     
     
       5. The ink jet recording apparatus as claimed in  claim 4 , wherein the float member is movable vertically in a gravity direction with a support shaft arranged in said sub-tank unit as a rotation center. 
     
     
       6. The ink jet recording apparatus as claimed in  claim 4 , wherein the float member includes a box member that is formed by one side face and a peripheral side face molded integrally with the one side face to have an opening part in an opposite face side, and a plate-like lid jointed to the opening part of the box member close the box member. 
     
     
       7. The ink jet recording apparatus as claimed in  claim 4 , 
       wherein the float member includes a quadrate volume body formed at a position away from a support shaft as viewed in a horizontal direction, and a trilateral volume body having a bottom face formed substantially linearly from a bottom face of the quadrate volume body to the support shaft side in the proximity of the support shaft.  
     
     
       8. The ink jet recording apparatus as claimed in  claim 4 , wherein the float member is formed with at least a pair of positioning pins, projected to respective outsides of the float member in a horizontal direction, each for holding a predetermined gap between the float member and an inner wall of said sub-tank unit. 
     
     
       9. The ink jet recording apparatus as claimed in  claim 8 , wherein each of the positioning pins is formed so as to hold a distance of at least 1 mm or more between the float member and the inner wall of said sub-tank unit. 
     
     
       10. The ink jet recording apparatus as claimed in  claim 4 , wherein the valve mechanism for opening and closing the exhaust port is located at an intermediate point between a center of gravity of buoyancy of the float member and the support shaft. 
     
     
       11. The ink jet recording apparatus as claimed in  claim 4 , wherein the valve mechanism for opening and closing the exhaust port closes an end face of a valve member in a horizontal state when the buoyancy of the float member reaches maximum buoyancy. 
     
     
       12. The ink jet recording apparatus as claimed in  claim 1 , wherein said ink replenishment unit includes an ink droplet discharge port communicating with the main tank through a self-seal valve, and an air suction port. 
     
     
       13. The ink jet recording apparatus as claimed in  claim 1 , wherein said sub-tank unit includes an atmospheric communication port, and said ink replenishment unit includes a valve for sealing the atmospheric communication port. 
     
     
       14. The ink jet recording apparatus as claimed in  claim 1 , wherein the valve mechanism for opening and closing the exhaust port is provided for each ink storage chamber, and wherein the negative pressure generation means is formed as a single unit. 
     
     
       15. The ink jet recording apparatus as claimed in  claim 1  or  2 , wherein an ink flow exit part of the main tank is positioned lower in gravity direction than the ink injection port of said sub-tank unit, or is adapted to cause negative pressure to act on the ink injection port. 
     
     
       16. The ink jet recording apparatus as claimed in  claim 1 , wherein the valve mechanism for opening and closing the exhaust port includes a flexible thin film forming a space communicating with the negative pressure generation means, and an opening that is formed in a part of the flexible thin film and that is closed by a seal member arranged on a float member when said sub-tank unit is filled with a given amount of ink, and wherein a communication part with the negative pressure generation means is sealed with the flexible thin film which is contracted upon the opening is closed by the seal member. 
     
     
       17. The ink jet recording apparatus as claimed in  claim 1  or  16 , wherein said sub-tank unit and said ink replenishment unit have alignment means capable of matching ink supply passages of both said sub-tank unit and said ink replenishment unit with each other when they are engaged with each other. 
     
     
       18. The ink jet recording apparatus as claimed in  claim 17 , wherein: 
       said ink replenishment unit is connected to the main tank by a tube and is arranged movably in a vertical direction and a horizontal direction,  
       said sub-tank unit is mounted on the carriage so as to be moved to and stopped at a predetermined ink supply area,  
       the alignment means includes a guide rib on an engagement side of said ink replenishment unit, and a guide member on said sub-tank unit, and  
       said ink replenishment unit and said sub-tank unit are positioned to each other by contacting the guide rib with the guide member during movement of the ink replenishment unit to the sub-tank unit.  
     
     
       19. The ink jet recording apparatus as claimed in  claim 18 , further comprising: 
       guide means provided at at least two locations between said ink replenishment unit and an attitude maintaining member, each of the guide means including an elongated hole formed in a direction orthogonal to a movement direction, and a protruded part inserted slidably into the elongated hole,  
       wherein said ink replenishment unit is supported movably relative to the attitude maintaining member in the direction orthogonal to the movement direction.  
     
     
       20. The ink jet recording apparatus as claimed in any of  claims 18  to  19 , wherein: 
       said ink replenishment unit is supported movably up and down by guide projections inserted into elongated grooves formed in a vertical direction at left and right end parts, and  
       each of the elongated grooves in said ink replenishment unit are partially formed with a spread section to provide a predetermined allowance with respect to the guide projection during movement of said ink replenishment unit to said sub-tank unit.  
     
     
       21. The ink jet recording apparatus as claimed in any of  claims 18  to  20 , wherein the guide rib and the guide member forming the alignment means are arranged in orthogonal relation to each other to align said ink replenishment unit in one horizontal direction and in another horizontal direction orthogonal thereto. 
     
     
       22. The ink jet recording apparatus as claimed in  claim 17 , wherein: 
       said ink replenishment unit is supported movably in a direction orthogonal to a movement direction by an attitude maintaining member that is made movable in a vertical direction by at least a pair of support shafts,  
       said ink replenishment unit is also supported by the support shafts in a state in which the support shafts are passed through elongated holes formed in parallel to the movement direction, and  
       said elongated holes are partially formed with spread sections enlarged to provide a predetermined allowance with respect to the support shaft during the movement to said sub-tank unit.  
     
     
       23. The ink jet recording apparatus as claimed in  claim 22 , wherein said ink replenishment unit is driven in a vertical direction by a drive member that is engaged with an engagement hole formed in a part of said ink replenishment unit and that is moved up and down by the rotation operation of a cam member. 
     
     
       24. The ink jet recording apparatus as claimed in  claim 23 , 
       wherein one of the pair of support shafts is a drive shaft for rotationally driving the cam member.  
     
     
       25. The ink jet recording apparatus as claimed in  claim 1  or  26 , wherein an ink supply valve is closed in a state in which power is off. 
     
     
       26. An ink jet recording apparatus, comprising: 
       a sub-tank unit, mounted on a carriage, for supplying ink to an ink jet record head; and  
       an ink replenishment unit that is connected to a main tank installed in a housing by a conduit and that is connectable to and disconnectable from said sub-tank unit, wherein said sub-tank unit comprises a single container divided into a plurality of chambers by a wall or walls;  
       said sub-tank unit has, for each of the chambers, an ink injection port and an exhaust port communicating with a respective ink storage chamber through self-seal type valve means, and a valve mechanism for opening and closing the ink injection port or the exhaust port based on a liquid level of ink, wherein ink is supplied to the respective ink storage chamber by negative pressure produced by sucking air through the exhaust port.  
     
     
       27. The ink jet recording apparatus as claimed in  claim 1  or  26 , wherein the valve mechanism for opening and closing the exhaust port includes a valve member having a valve opening communicating with the negative pressure generation means, and a seal member, arranged on the float member, for opening and closing the opening of the valve member. 
     
     
       28. The ink jet recording apparatus as claimed in  claim 27 , wherein the valve mechanism for opening and closing the exhaust port is molded of a soft material, and the seal member is molded of a hard material. 
     
     
       29. The ink jet recording apparatus as claimed in  claim 27 , wherein the valve mechanism for opening and closing the exhaust port is molded of soft elastomer. 
     
     
       30. The ink jet recording apparatus as claimed in  claim 27 , wherein the valve member is formed into a trapezoidal shape in cross section in a vertical direction, and is formed at a center vertically with the valve opening communicating with the negative pressure generation means, and wherein the seal member abuts a short side portion of the trapezoidal shape in cross section. 
     
     
       31. The ink jet recording apparatus as claimed in  claim 30 , wherein the valve member is designed so that the valve opening communicating with the negative pressure generation means is enlarged in a triangular manner in cross section in a long side portion of the trapezoidal shape in cross section. 
     
     
       32. The ink jet recording apparatus as claimed in  claim 30 , wherein the valve member is molded integrally with an inner peripheral surface of an annular fixing member, and is attached to said sub-tank unit through the fixing member. 
     
     
       33. The ink jet recording apparatus as claimed in  claim 30 , wherein the valve member is surrounded by a tubular rib for preventing ink from being deposited. 
     
     
       34. The ink jet recording apparatus as claimed in  claim 1  or  26 , wherein said ink replenishment unit includes: 
       a slide plate moved up and down;  
       a connection suction passage formed on the slide plate, and connected at one end to the negative pressure generating means and at the other end to said sub-tank unit, and  
       atmospheric communication port opening and closing means, formed on the slide plate, for opening and closing the atmospheric communication port.  
     
     
       35. The ink jet recording apparatus as claimed in  claim 34 , wherein up and down movement of the slide plate establishes a first state in which the connection suction passage is not connected to said sub-tank unit and the atmospheric communication port is opened, a second state in which the connection suction passage is not connected to said sub-tank unit and the atmospheric communication port is closed, and a third state in which the connection suction passage is connected to said sub-tank unit and the atmospheric communication port is closed. 
     
     
       36. The ink jet recording apparatus as claimed in  claim 35 , wherein the atmospheric communication port opening and closing means is formed at the same height as a tip part of the connection suction passage connected to said sub-tank unit, wherein the atmospheric communication port provided in said sub-tank unit is formed at a height different from that of a tip part of the suction passage on the sub-tank unit side, and wherein one of the first to third states is selected as the slide plate is moved up and down. 
     
     
       37. The ink jet recording apparatus as claimed in  claim 35 , wherein the atmospheric communication port opening and closing means is formed at a height different from that of a tip part of the connection suction passage connected to said sub-tank unit, and wherein one of the first to third states is selected as the slide plate is moved up and down. 
     
     
       38. The ink jet recording apparatus as claimed in  claim 37 , wherein the atmospheric communication port opening and closing means is a press member provided to elastically move a closing member formed movably up and down with respect to the slide plate. 
     
     
       39. The ink jet recording apparatus as claimed in  claim 37  or  36 , wherein the atmospheric communication port in said sub-tank unit is formed with a valve body that is movable up and down, that opens the atmospheric communication port at an upward position and that closes the atmospheric communication port when the valve body is moved down, and wherein the valve body is moved down by the atmospheric communication port opening and closing means provided in a lower end part of the slide plate to closing the atmospheric communication port. 
     
     
       40. The ink jet recording apparatus as claimed in  claim 1  or  26 , further including valve units for enabling the ink to flow in a state in which said sub-tank unit and said ink replenishment unit are connected, and automatically closing connection parts of said sub-tank unit and said ink replenishment unit in a state in which they are disconnected. 
     
     
       41. The ink jet recording apparatus as claimed in  claim 40 , wherein one of the valve units is disposed in an ink supply area positioned above a movement path of the carriage, and the other valve unit is mounted on the carriage, and wherein the sub-tank unit and the ink replenishment unit can be connected to each other by the two valve units in a state in which the carriage is positioned in the ink supply area. 
     
     
       42. The ink jet recording apparatus as claimed in  claim 40  or  41 , wherein each of the valve units includes a push rod disposed in a cylindrical case and urged in a projection direction, and a seal member made of a flexible material for closing the ink supply passage in a projected state of the push rod, and wherein movement of the pushing rods caused due to connection between the sub-tank unit and the ink replenishment unit makes flow of ink enabled. 
     
     
       43. The ink jet recording apparatus as claimed in  claim 40 , wherein a taper part is formed partially on at least one of the push rods of the valve units, and the taper part abuts the seal member in the projected state of the push rod. 
     
     
       44. The ink jet recording apparatus as claimed in any of  claims 40  to  43 , wherein the push rod in the cylindrical case is supported slidably in an axial direction by at least three fins projecting toward an axis center of the cylindrical case. 
     
     
       45. The ink jet recording apparatus as claimed in any of  claims 40  to  44 , wherein at least one of the seal members of the valve units is extended to a joint face of the cylindrical case. 
     
     
       46. The ink jet recording apparatus as claimed in  claim 45 , wherein the seal member is arranged on a joint face of at least one of the valve units, and after sealing isolating from outside air is established with the seal member arranged on the connection end face, the push rod is moved to forming an ink flow. 
     
     
       47. The ink jet recording apparatus as claimed in  claim 1  or  26 , wherein an air introduction port is closed in a state in which power is off. 
     
     
       48. The ink jet recording apparatus as claimed in  claim 1  or  26 , wherein an ink supply passage and an air introduction port are closed in a state in which power is off. 
     
     
       49. The ink jet recording apparatus as claimed in  claim 1  or  26 , wherein an air introduction port is opened if the pressure difference between said sub-tank unit and outside air exceeds a given value in a state in which power is off. 
     
     
       50. The ink jet recording apparatus as claimed in  claim 49 , wherein an ink supply valve is maintained closed even in a state in which the air introduction port is opened. 
     
     
       51. The ink jet recording apparatus as claimed in  claim 1  or  26 , wherein an air introduction port is opened prior to an ink supply port if the pressure difference between said sub-tank unit and outside air exceeds a given value in a state in which power is off. 
     
     
       52. The ink jet recording apparatus as claimed in  claim 51 , wherein an ink supply valve is maintained closed. 
     
     
       53. An ink jet recording apparatus comprising: 
       a sub-tank unit provided with a record head; and  
       a main tank capable of replenishing said sub-tank unit with ink,  
       wherein an ink storage chamber and the record head of said sub-tank unit are connected through backflow prevention means for enabling ink to flow into the record head from the ink storage chamber, and  
       wherein an ink replenishment unit for replenishing said sub-tank unit with ink from the main tank by reducing pressure in the ink storage chamber by negative pressure generation means is provided.  
     
     
       54. The ink jet recording apparatus as claimed in  claim 53 , wherein a carriage to which said sub-tank unit is attached is moved to a record area, an ink replenishment area, and a recovery position for recovering an ink droplet ejection capability. 
     
     
       55. The ink jet recording apparatus as claimed in  claim 54 , wherein the ink replenishment area and the recovery position are the same area. 
     
     
       56. The ink jet recording apparatus as claimed in  claim 54 , wherein the ink replenishment area is more distant from the record area than the recovery position. 
     
     
       57. The ink jet recording apparatus as claimed in  claim 54  or  55 , wherein said sub-tank unit is allowed to communicate with said main tank in the ink replenishment area and at the recovery position. 
     
     
       58. An ink jet recording apparatus as claimed in any of  claim 1 ,  26 , or  53 , 
       wherein first and second connection parts for forming an ink flow passage between said sub-tank unit and the main tank are arranged in a conduit, and  
       wherein first and second ink seal means opened if the first and second connection parts are connected to each other are provided.  
     
     
       59. The ink jet recording apparatus as claimed in  claim 58 , wherein the first ink seal means is designed so that a hollow ink flow passage member is slidably inserted into a first seal hole of a first seal body, and that an ink small hole opened in the ink flow passage member is exposed from the first seal body to open the ink flow passage only when the first connection part is connected to the second connection part. 
     
     
       60. The ink jet recording apparatus as claimed in  claim 59 , wherein when the first and second connection parts are connected, the shaft part of the slide shaft is urged by the ink flow passage member to open the ink flow passage. 
     
     
       61. The ink jet recording apparatus as claimed in  claim 60 , wherein the ink flow passage member is formed with a conical convex part, and the shaft part of the slide shaft is formed with a conical concave part engaging the conical convex part. 
     
     
       62. The ink jet recording apparatus as claimed in  claim 58 , wherein the second ink seal means includes a second seal body and a slide shaft having a shaft part inserted slidably into a second seal hole of the second seal body, and the shaft part is projected from the second seal hole to open the ink flow passage only when the second connection part is connected to the first connection part. 
     
     
       63. The ink jet recording apparatus as claimed in any of  claim 1 ,  26 , or  53 , further comprising pressure detection means, arranged in a flow passage from for communication from said sub-tank unit to the negative pressure generation means, for detecting a predetermined or more pressure drop, wherein ink replenishment completion is detected based on a signal of the pressure detection means. 
     
     
       64. The ink jet recording apparatus as claimed in any of  claim 1 ,  26 , or  53 , further comprising pressure detection means connected to a flow passage between the main tank and said sub-tank unit, for generating electric output upon detection of a predetermined or more pressure drop in the flow passage, wherein an attachment state of the main tank is detected based on the electric output of the pressure detection means. 
     
     
       65. The ink jet recording apparatus as claimed in  claim 63  or  64 , wherein the pressure detection means includes a flexible displacement member that forms a part of the flow passage and that is displaceable in association with pressure change in the flow passage, a spring member, added to the displacement member, for urging the displacement member in a direction opposite to a direction in which the displacement member is displaced in association with the pressure drop in the flow passage, and displacement detection means for detecting displacement of the displacement member. 
     
     
       66. A sub-tank unit for an ink jet recording apparatus, adapted to be mounted on a carriage, to be connectable to and disconnectable from a main tank installed in a housing side by a conduit, to receive ink supplied from an ink replenishment unit in an ink storage chamber and to supply ink to an ink jet record head, said sub-tank unit comprising: 
       an ink injection port and an exhaust port communicating with an ink storage chamber through self-seal type valve means, and  
       a valve mechanism for opening and closing the ink injection port or the exhaust port based on a liquid level of ink,  
       wherein said sub-tank unit receives supply of negative pressure in the exhaust port, to thereby receive supply of ink in the ink storage chamber.  
     
     
       67. The sub-tank unit for an ink jet recording apparatus as claimed in  claim 66 , further comprising a float that stops ink replenishment at a stage at which the ink storage chamber is replenished with the ink up to a predetermined value of ink amount. 
     
     
       68. The sub-tank unit for an ink jet recording apparatus as claimed in  claim 67 , wherein at least a part of the float is formed of an electric conductive material, and a move-up of the float is detected electrically. 
     
     
       69. The sub-tank unit for an ink jet recording apparatus as claimed in  claim 68 , wherein the ink storage chamber and the record head are communicated with each other through backflow prevention means for enabling the ink to flow into the record head from the ink storage chamber. 
     
     
       70. A sub-tank unit for an ink jet recording apparatus, adapted to be mounted on a carriage, to be connectable to and disconnectable from a main tank installed in a housing side by a conduit, to receive ink supplied from an ink replenishment unit in an ink storage chamber and to supply ink to an ink jet record head, said sub-tank unit comprising: 
       ink flow passage means for guiding the ink supplied from the main tank into the ink storage chamber, and  
       negative pressure generation means for supplying the ink to the record head,  
       wherein the ink flow passage means and the negative pressure generation means are located in the ink storage chamber,  
       wherein an ink flow-out port of said ink flow passage means and an ink flow-in port of said negative pressure generation means are arranged to face each other through such a gap as to allow air bubbles to be moved upward.  
     
     
       71. An ink droplet ejection capability recovery method for a recording head of an ink jet recording apparatus comprising a sub-tank unit provided with a record head and a main tank capable of replenishing the sub-tank unit with ink, the method comprising: 
       determining if an ink remaining amount in the sub-tank unit is greater than a recovery operation consumption amount,  
       replenishing the sub-tank unit with the ink from the main tank when it is determined that the ink remaining amount in the sub-tank unit is less than or equal to the recovery operation consumption amount, and  
       performing a recovery operation after the replenishing step is complete.  
     
     
       72. The ink droplet ejection capability recovery method as claimed in  claim 71 , wherein after the ink is previously discharged from the sub-tank unit, the sub-tank unit is replenished with the ink from the main tank and then the recovery operation is carried out. 
     
     
       73. The ink droplet ejection capability recovery method as claimed in  claim 71 , wherein an ink consumption state in the sub-tank unit is detected, and the recovery operation is carried out at least once or more as long as ink exists.